Kathryn McDonough testifies Tuesday in Strafford County Superior Court in Dover. McDonough is the state's key witness against her former boyfriend Seth Mazzaglia charged with first-degree murder in the 2012 death of Elizabeth "Lizzi" Marriott of Westborough, Mass. (POOL PHOTO BY RICH BEAUCHESNE/PORTSMOUTH HERALD)

DOVER — Kathryn “Kat” McDonough, the former live-in girlfriend of accused murderer Seth Mazzaglia, took the stand first thing Tuesday morning at Strafford County Superior Court and immediately testified that it was Mazzaglia who killed Elizabeth "Lizzi" Marriott in October 2012.

Mazzaglia, 31, faces charges of first- and second-degree murder in the Oct. 9, 2012 death of 19-year-old UNH student Marriott. McDonough, now 20, was in the Sawyer Mills home she shared with Mazzaglia on the night that Marriott died there after a game of strip poker.

In last Wednesday’s opening statements, defense attorney Joachim Barth told jurors it was McDonough, not Mazzaglia, who killed Marriott that night during sexual acts involving bondage and erotic asphyxiation. Prosecutors have said Mazzaglia strangled Marriott while raping her limp body.

McDonough is serving a 1½- to three-year prison term after pleading guilty last July to charges including witness tampering and hindering the investigation.

Prosecutor Peter Hinckley’s first question to McDonough on Tuesday morning was direct.

“Ms. McDonough, who killed Elizabeth Marriott?” he asked, immediately after she was sworn in and identified herself to the jury.

“Seth Mazzaglia,” she replied, before testifying that Mazzaglia strangled Marriott with a rope and raped her limp body.

Hinckley also asked McDonough if she helped “cover up” Marriott’s death and rape afterward.

“Yes, I did,” McDonough said.

After the stunning start to the fifth day of the murder trial that has horrified and riveted Strafford County and New Hampshire, Hinckley moved his questioning to 2011, when McDonough and Mazzaglia met, and began questioning her about the origin and early days of their relationship.

‘Soulmates beyond time’

McDonough said she met Mazzaglia in the spring of 2011, when they were in a theater production together in Portsmouth. She was 17 and he was 28. The relationship became romantic and sexual in October 2011, she said, when they were both working at a haunted house.

“He was very kind, very creative. He would always drive me around whenever I needed a ride…he would always tell me how special I was and how beautiful I was,” McDonough said, describing the beginning of their romantic relationship. “He encouraged the things I liked to do, like theater and art. …He made me feel like I was very important, like I was the one for him.”

Mazzaglia’s impact on her life quickly mushroomed, according to McDonough’s testimony.

Hinckley displayed a series of Facebook conversations between the two, in which Mazzaglia adopted different personas – such as “Dark Heart” and “Doomsday” – urged McDonough to move in with him and encouraged her to “cut ties” with her parents.

Mazzaglia referred in the messages to her father as a “waste of oxygen” and to her mother, repeatedly, as “mother dragon.”

McDonough said Mazzaglia’s use of several personas resonated with her, because she had done similar things herself since elementary school.

“When I was younger, I was dealing with a lot of trouble in my household growing up, and I was trying to figure out who I was as a person,” she said. “I was very shy…so I created almost an alter-ego, a persona. …Someone who was very strong.”

McDonough said her personas, such as “Skarlet” – changing the “c” to a “k” was Mazzaglia’s idea, she said – would help her “get through a lot of the things (she) had to get through,” and took on greater significance after she met Mazzaglia.

“When I met Seth, he told me he had the same thing…and it kind of fit what I was doing, so I went with it,” she said, adding that it strengthened her attraction to him. “To find out that someone had something that was even more real than mine…it made me feel like I wasn’t alone.”

McDonough said she turned 18 in November 2011 and moved in with Mazzaglia in February 2012, despite her initial plans to wait until after she graduated that June.

McDonough said she believed that Mazzaglia had spiritual powers, could see into the future – through his “Cyrus” persona – and could affect forces of nature.

“He said that we were soulmates beyond time, like in past lives,” she said. “He said that my mom was trying to keep us from being together, even on a subconscious, spiritual level.”

Hinckley displayed one message in which Mazzaglia wrote to McDonough that “you have every right to call (your mother) an irresponsible parent and walk out of there and have me pick you up.”

Hinckley also asked McDonough about Facebook messages in which Mazzaglia would discuss tarot card readings involving “death” and “darkness.”

McDonough said she had only a passing interest in tarot cards before she met Mazzaglia.

“Once I started dating him, he actually gave me a deck…and told me that I would be good at it,” she said.

Tarot cards became an important aspect of their relationship and even her decision-making for significant life choices, she said.

“He was almost always the one reading the cards,” McDonough said. “At one point, when he read a deck, it said that I really needed to move out of my mom’s house quickly.”

In many of the Facebook messages Hinckley showed and read out loud Tuesday morning, Mazzaglia wrote that spiritual forces and entities were influencing and would be affected by McDonough’s life decisions, such as whether to take an EMT class, move to Florida, attend college or move in with him.

McDonough said she eventually enrolled in an EMT class in Durham after Mazzaglia’s urging, paying for it with about $700 from her savings. Mazzaglia also took the class and they both passed, she said.

Hinckley asked whether CPR treatment was part of the class, for someone with breathing problems. McDonough said it was.

'Controlling’ relationship

Hinckley also asked McDonough about Facebook messages in which Mazzaglia wrote about “keeping the darkness in check” and ways that McDonough could keep him, Hinckley said, “from straying with other women.”

McDonough said Mazzaglia told her that “bringing in other women” could help in that regard.

“He made it seem like such a good thing, but at the time, I didn’t want to share him,” McDonough said. She later added that she eventually consented to the idea, “mostly to please him…but every once in a while it seemed intriguing.”

“They were usually my friends,” McDonough said of the other women she would bring into her relationship with Mazzaglia. “From high school.”

Hinckley asked if she would “often serve as an instructor or teacher” in sexual acts involving bondage and domination with her friends. McDonough said she would.

Guided by Hinckley’s questioning, McDonough described her life with Mazzaglia from February to October 2012 as mostly spent in their apartment, spending “almost all day” with him on a daily basis and relatively little interaction with her own friends or time outside of their home.

“I would ask to go different places, like different stores I wanted to check out” or outdoor activities, she said. “We didn’t end up doing many of them.”

McDonough agreed at various times when Hinckley asked if Mazzaglia was “controlling” or “protective” of her, especially regarding time she spent with her family or with male friends. But she also said she continued to love him and his “caring” nature continued, as well.

McDonough gave most of her testimony in a flat, calm voice mostly without emotion, though she sounded sadly resigned in some responses. When Hinckley asked McDonough if she still adopted different personas, her reply was simple.

“No,” she said.

Dominance and submission

McDonough agreed when Hinckley asked if sex was “a central part of her relationship” with Mazzaglia.

“It was pretty consistent. At least once a day, if not six or nine times a day,” she said. “It was a BDSM relationship, based on dominant and submissive. Where one side of the party has control over the other.”

McDonough said the roles were strongly defined.

“I was the submissive. He was the dominant,” she said.

McDonough said she and Mazzaglia engaged in sex with different levels of dominance, including “submissive” and “slave.”

“A submissive has more say,” she said. “Their pleasure is also taken into consideration, even though it’s not as much, whereas a slave…it’s completely one-sided.”

She said Mazzaglia would sometimes tie her up with “a soft, white cotton rope” or other restraints such as belts or collars, and always had control of their activities. He frequently would tie her up tightly enough to leave bruises or rope indentations on her skin, she said.

“There was ‘master,’ ‘lord,’ things like that,” she said, citing how she would refer to him.

McDonough said Mazzaglia routinely used “derogatory sexual terms” to refer to her. “Like ‘slut,’ and ‘whore,’ things like that,” she said.

Hinckley asked McDonough to describe the use of “breath control” in sex.

“Limiting the air intake to one other person,” she said. “Usually he’d put his hands around my neck. …It wasn’t very often.”

McDonough said she occasionally had a rope tied around her neck during sex with Mazzaglia, “and he would pull on it.”

“I never did it to him,” she said.

Hinckley asked whether they ever used “safe words” to indicate when breath control, restraints or other violent sexual activities should be stopped.

“We didn’t have a safe word at all,” she said.

McDonough also said she and Mazzaglia sometimes had other people over to the apartment, to engage in group sex or sex while others were watching. Hinckley asked about their use of the term “alpha.”

“We both used the term, but he was the alpha,” she said. “If we had a big group of people, I would still be the top woman of the group.”

She agreed when Hinckley asked if Mazzaglia was always the “overall alpha,” regardless of the situation.

“He would have control of what was happening, but I could ask him if we could do something different,” she said.

Hinckley ended the morning session of court proceedings by projecting on a large screen an erotic note that McDonough said she wrote to Mazzaglia, expressing her willingness to submit to him sexually.

She said a response below the note was written by Mazzaglia.

“To my willing, I will dominate you, brutally, without mercy,” the response read. “I am your lord, and I will use you to your exhaustion.”

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